This invention relates generally to manually operated gas delivery systems for oxygen or anesthetic gas to patients through a face mask or endotracheal tube, and more particularly to such gas delivery systems using a flexible gas reservoir bag.
Breathing quantity and quality, and therefore, related respiratory support as may be required, include three separate modes of breathing; (1) "spontaneous breathing" (normal and unassisted respiration); (2) "assisted breathing" (the addition of positive pressure during the inspiratory phase of respiration to provide an adequate volume of oxygen to the lungs); and (3) "controlled breathing" (providing both an adequate rate of breathing and an adequate inspiratory positive pressure in order to sufficiently oxygenate the lungs).
Gas supply systems for providing positive inspiratory pressure in the past generally have utilized a self-expanding semi-rigid gas reservoir bag which may be manually squeezed to supply gas through a face mask, or endotracheal tube, to the patient's lungs. Such prior devices are generally known as resuscitators and are often used by various persons in providing pre-hospital emergency medical care.
The greatest asset of such resuscitators is the ability to provide atmospheric air under positive pressure to a patient's lungs. Such resuscitators, however, are primarily of use for controlled breathing and are poorly suited for assisted breathing. These resuscitators have no applicability in situations involving spontaneous breathing.
Such resuscitators have utilized various types of valves or diaphragms for directing inspiratory ambient air, with or without various oxygen enriching devices, to a patient or for the venting of exhaled gases from a patient. Such devices presented problems including the addition of resistance to a patient's inspiratory and expiratory effort and increasing the complexity and cost of the use of the breathing systems. Because such resuscitators are often transported, size is an important consideration. In addition, because of the need for a sterile aseptic environment, such resuscitators must be sterilized after each use. Often, such devices must be dissembled for sterilization and then reassembled for reuse. Such practices increase both the cost of use and the risk of harm to a patient through a mistake in reassembly or through contamination. Such problems are aggravated by the complexity of such devices. Furthermore, the only way to provide pure oxygen with these devices is to employ a secondary bag or reservoir, receiving an oxygen supply, and which is in communication with the fluid intake means of the self-expanding bag.
Devices also exist for providing supplemental oxygen to a patient who is breathing spontaneously. Such devices, however, are not useful in situations in which the patient's condition requires assisted or controlled breathing. Additionally, these devices provide little, if any, monitoring quality of breathing as may be observed by the rhythmic expansion and contraction of a flexible reservoir bag.
While flexible gas reservoir bags have been utilized heretofore in resuscitators with various adjustable valve means at one end of the bag to control a vent thereat for varying the fluid pressure within the interior of the gas bag, such valve means have been relatively complex or difficult to operate manually with the use of any one hand of an operator. Further, such valve means have not normally included visual indicators directly adjacent the valve means for indicating the pressure being applied to a patient's lungs by a particular setting of the valve means in order to easily adapt the resuscitator for use with different types of breathing. And, while these devices function well for the spontaneously breathing patient, when oxygen is the sole gas entering the system, the absence of an oxygen dilution capability will subject the patient to the hazards and risks of breathing pure oxygen. This type of administration is especially perilous for post-operative patients an patients with pre-existing chronic obstructive pulmonary disease.